﻿// Copyright 2017 the original author or authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

using System;
using System.Collections.Concurrent;

namespace Steeltoe.Messaging.Core
{
    public class CachingDestinationResolverProxy<D> : IDestinationResolver<D>
    {
        private readonly ConcurrentDictionary<string, D> _resolvedDestinationCache = new ConcurrentDictionary<string, D>();

        private IDestinationResolver<D> _targetDestinationResolver;

        public CachingDestinationResolverProxy(IDestinationResolver<D> targetDestinationResolver)
        {
            if (targetDestinationResolver == null)
            {
                throw new ArgumentNullException(nameof(targetDestinationResolver));
            }

            _targetDestinationResolver = targetDestinationResolver;
        }

        public D ResolveDestination(string name)
        {
            _resolvedDestinationCache.TryGetValue(name, out var destination);
            if (destination == null)
            {
                destination = _targetDestinationResolver.ResolveDestination(name);
                _resolvedDestinationCache.TryAdd(name, destination);
            }

            return destination;
        }

        object IDestinationResolver.ResolveDestination(string name)
        {
            var result = ResolveDestination(name);
            return result;
        }
    }
}
